Glucagon is a small polypeptide hormone having 29 amino acids. It is synthesized in pancreas islets and exhibits biological action which is the converse of insulin, thereby permitting control of blood glucose level both through glycogenolysis and gluconeogenesis.
The amino acid sequence of porcine glucagon was determined by Bromer, W. W., Sinn, L., and Behrens, O. K., J. Am. Chem. Soc. 79, 2801-2805 (1957). Subsequent studies have established that glucagon isolated from other mammalian species is identical to that of porcine glucagon.
Glucagon (molecular weight, 3485 daltons) is synthesized in the A cells of pancreas islets from a precursor molecule estimated to have a molecular weight of about 18,000 to 19,000 daltons. The preprohormone is converted to glucagon through a series of proteolytic cleavages.
Commercial glucagon is available by isolation from bovine or porcine pancreas as a side product during insulin extraction. In extraction of pancreatic insulin, a salt cake can be recovered which contains a predominant quantity of the pancreas-originated glucagon. This salt cake, designated the glucagon salt cake, represents the starting material for the process which is herein defined and which represents the present invention.